Physical barriers - are they just for show?

I’m trying to understand if/how physical barriers - trees, rocks, walls, etc. - work in LE. It seems that any enemy with a ranged/AoE attack can simply ignore these “obstacles” to attack me on the other side.

Is this by design, or is it a bug?

EDIT: the barriers do seem to affect me and any minions I may have. The worse offenders by far are the Cemeteries/Tombs.